Loud speaker element



March 8, 1932. E. s. PRIDHAM LOUD SPEAKER ELEMENT Filed Sept. 9. 1929 2 Sheets-Sheet INVENTQR.

By PM a ATTORNEYS.

March 8, 1932. E. s. PRIDHA M LOUD SPT=/-\KER ELEMENT Filed Sept. 9. 1929 2 Sheets-Sheet I I N V EN TOR.

BY P j VAL/W 1 7 ATTORNEYS.

Patented Mar. 8, 1932 UNITED STATES PATENT OFFICE EDWIN S. PRIDHAM, OF OAKLANI), CALIFORNIA, ASSIGNOR TO THE MAGNAVOX COM- PANY, OF OAKLAND, CALIFORNIA, A CORPORATION OF ARIZONA LOUD SPEAKER ELEMENT Application filed September 9, 1929. Serial No. 391,295.

My present invention relates to loud speakers and more particularly to an electro-magnetically operated diaphragm therefor.

An object of my invention is to provide a novel, inexpensive and practical type of. diaphragm for loud speakers of the so-called dynamic type.

A further object of my invention is to provide in combination with an electromagnetically actuated cone diaphragm, a centering and supporting member which will permit the cone to vibratefreely in response to forces applied thereto.

Another object of my invention is to provide a coil mounting and centering means for loud speaker diaphragms of the cone type which is light, strong and exceedingly durable.

A further object of my invention is to provide a method of manufacturing loudspeaker diaphragms of the cone type in whlch the diaphragm, coil supporting means and the diaphragm centering means may be assembled in a unit at substantially the same time, so that the number of operations thereupon will be reduced to a minimum.

In the past, it has been the general practice to attach to the apex of an open cone, by anysuitable means, a cylindrical member about which the actuating coil is wound.

'The cylindrical member in most cases has been provided with an annular groove thereabout through which the turns of an electromagnetic coil may be disposed. With such a device, it will be seen'that the operation of manufacturing the cylindrical member is complicated in that, due to its frail'zcharacter,

there is experienced great difficulty in turning an annular groove in the outer surface thereof. In prior art devices there have also been provided various types of flexible cen-.

tering means for these coil supports. The centering means in the past have been made up as separate units and later attached to the cone at the point where the coil supporting cylindrical member joins therewith. With the above assembly, it will be seen that there are three distinct parts which have to be handled in completing the assembly and for this reason diaphragms of the type contemplated by my invention have in the past, because of their delicate character, been very expensive to produce.

In order to overcome the above difliculties and at the same time produce a superior product, I propose to provide a coil supporting means of novel design upon which the centering means is permanently secured during the support forming operation and then later attached to the conical diaphragm in a new and novel manner, as will hereinafter appear.

For a better understanding of my invention, reference should be had to the following description, taken in connection with the accompanying drawings, wherein I have shown by way of illustration and not of limitation a preferred type of device.

In these drawings Fig. 1 is a fragmentary side elevation, partially in section, showing the details of construction of my improved diaphragm and coil support.

Fig. 2 is an end elevation projected from Fig. 1.

Figs. 3, 4, and 5 are, respectively, a reinforcing member, a cone, and the coil support with its centering means and terminals mounted thereupon. These three views constitute an exploded illustration of the complete assembly.

Fig. 6 is a perspective view of my improved coil supporting and centering means showing the manner of constructing same.

Fig. 7 is an enlarged, fragmentary view, I

partially in section, showing a further embodiment of my invention.

Fig. 8 is an exploded view showing in perspective the several major parts of the diaphragm illustrated in Fig.

By referring to Figs. 1 and 2, it will be seen that the cone diaphragm designated by in the art to which my invention appertains.

Projecting through the opening in the apex of the cone 10, there is shown a cupped disc 14 having an annular rim. When this disc 14: is forced through the opening in the cone, it will telescope with the cylindrical member 11 and flare the edge of the cone outwardly and against the interior surface of the cylindrical member 11 so that the parts will be securely held together. While the member 14 is shown in the drawings in the form of a cupped disc, I desire to have it understood. that this configuration is not essential, as an annular ring suitably flanged to provide stifl'ness will work equally well and, in fact, it is believed in some instances a flanged annular ring of the above character is equally as effective and rigid as a complete disc type of element. In practice, I have found that a ring formed of aluminum havin a thickness of only five-thousandths of an inch when properly flanged provides a very effective reinforcing and securing means for the cone and coil support.

At the apex of the cone 10, where the member 14 projects therethrough,-I have, in order to facilitate an expansion of this portion of the cone, serrated the edge so that the cone may be readily flared. I desire to have it understood, however, that with diaphragms of certain compositions this serration at this point may be found wholly unnecessary.

In order to secure the flexible support 12 and the coil 13 against displacement on the cylindrical member 11, I propose to wind strips 15, 16 and 17 therea 'out at suitably spaced points so that annular recesses will be provided therein into which these elements may be located. The strips 15 and 16, it will be noted, are disposed on opposite sides of the flexible centering support 12 so that the latter is held firmly therebetween and the strip 17 is shownas wound about the cylindrical member 11 at a point displaced from the strip 16 so as to provide an annular groove about the cylindrical member 11 into which the coil 13 may be wound, the strips 16 and 17 forming in this instance what might be termed .flanges which retain the coil 13 against axial displacement.

Mounted upon the cone end of the cylindrical member 11 and having tongues projecting between it and the outer surface of the cone, I show a pair of terminals18 to which the ends of the coil 13 are connected. These terminals 18 in turn are connected with an external circuit by means of suitable flexible lead 19 which may be soldered or otherwise attched thereto.

By referring more particularly to Fig. 2, it will be seen that the supporting member 12 is provided" with an annular portion 20 which fits tightly about the cylindrical member 11.

Projecting outwardly from the annular mem-.

ber 20 there is also shown a pair of oppositely disposed radially extending arms 21 which connect with an outer annular portion 22. The annular portion 22 is extended outwardly at points midway between the arms 21 and is provided with suitable openings 23 by means of which it may be secured to a fixed support- 1ng means.

In producing a diaphragm in accordance with my invention, I proceed as follows: After providing a suitable mandrel upon which the cylindrical member 11 may be supported for rotation, I slip the supporting member 12 thereover. This member, by reason of its internal diameter, is such that it will serve to hold the cylindrical member upon the mandrel. I next aflix three strips of adhesively treated material to the cylindrical portion 11 and then rotate the mandrel so that the strips 15, 16 and 17 will be simultaneously wound thereabout.

In Fig. 6, my improved coil support and centering means is shown as partially completed. n this figure of the drawing, it will be noted that the strips 15, 16 and 17 are cut on a bias, each with respect to the others. This detail has been found to be desirable, as it results in the joints in the wrapped strips falling at different radially displaced points and therefore avoids the presence of any weakness which would be present if the joints were all made in a line along the cylinder. In this connection, the strips 15, 16 and 17 are also started upon the cylinder 11 at radially spaced points-so that each flange will contain a uniform number of complete turns.

During the assembling of these parts, it is to be understood that a suitable cement or other adhesive is generously used between the parts so that when the whole is dried,

the assembly will constitute a single unit.

When the unit is completed, as illustrated in Fig. 5, the terminal clips 18 are placed over the edge of the cylindrical member 11 with their tongue portions projecting inside of the cylinder. These projecting tongue portions are then crimped so that a slight clamping engagement will be obtained which will serve to hold the clips in place. This assembly is then placed upon-a suitable winding mandrel and the coil 13 is then wound upon the cylindrical member 11 between the flanges 16 and 17 After the winding operation has been completed, the ends of the coil so formed are then brought out through the flexible supporting member 12 and soldered to the terminals 18. The small end of the cone 10 is then placed in position upon the cylindrical member 11 in-a suitable jig which serves to center the parts accurately. The member 1 1 is then forced through the opening at the small end of the cone 10 so as to flare the serrated edge thereof outwardly and into intimate contact with the coil support. During this operation, it will also be understood that a suitable cement is generously applied to the various contactin surfaces. This assembly can then be remove from the ]1g and set to one side to dry, after which it may be assembled as a unit in the cone sup porting housing.

In order to facilitate a winding of the strips 17, it will be noted that, as shown in Fig. 1, these strips are made of a width substantially equal to that of the strips 15 and 16. After the coil 13 has been wound, however, it is the practice, since this flange is of a greater width than necessary, to cut off a portion of this flange as, for instance, at the dot and dash line designated by the numeral 24 in Fig. 5 of the drawings.

In order to provide a perfect cylindrical surface for the winding 13, I form the cylindrical member 11 of a single piece which is, as illustrated in Fig. 6 at the point 25, cut on a bias so that the abutting ends lie in a diagonal line through the cylinder. This form of construction provides an extremely light coil supporting means which may be disposed in a narrow air-gap.

By referring now to Sheet 2 of the drawings, where I have illustrated in Figs. 7 and 8 a further embodiment of my invention, it will be seen that the cone 10 is secured to a cylindrical member 26 in substantially the same manner as was the case in connection with the modification of my invention previously described. In this embodiment, it will be noted that the flexible supporting member 12 is, however, secured upon the cylindrical member 26 in different from that previously described. In this embodiment of my invention I have, instead of providing the taped strips 15 at the left hand side of the flexible member 12, flared the cylindrical member 26 outwardly along the conical surface of the cone 10. In order to facilitate an assembly of this character, I propose to provide serrations 27 upon the cone end of the cylindrical member 26, so that when the metallic ring, designated by the numeral 28, is inserted through the opening at the apex of the cone 10, the serrated end of the cylindrical member 26 will be flared outwardly in a ready manner and thus engage the side of the flexible member 12 in such a manner that the latter will be held firmly against the'strips 16 or other shoulder formed upon the cylindrical member 26 inany well. known manner.

In Figure 7 of the drawings I show the metallic ring 28. instead of a flanged disk 14, as illustrated in Figure 3. This rin 28 is provided with an outwardly exten ing flange 28' which engages the inside of the cone 10 and a smaller inwardly projecting flange 29 at its inner end. These flanges, in addition, to any other function they may have, also serve to stiffen the ring 28 and prevent it from being deformed in the assembly operation.

a manner somewhat By referring to Fig. 8 of the drawings, it will be seen that the serrations in the cylindrical member 26 extend member 26 to a point adjacent where the flexible member 12 is disposed. It will also be noted that the flexible member 12 is so designed that there is formed thereupon a perfectly annular ring portion 20 having an opening 29 into which the cylindrical member '26 will fit snugly so that when the serrations upon the cone 10 and the the cylindrical member wardly, as above suggested, by the insertion of the metallic ring 28 through the cone 10, the parts will-be forced outwardly into tight clamping engagement within the annular portion 20 of the flexible support 12 and where, as has also been suggested above, the, annular portion 20 is formed in a non-elastic material, the clamping occasioned by the insertion of the ring 28 will serve in conjunction with a suitable adhesive to permanently secure the coil support upon the cone and the flexible support 12 upon the cylindrical member.

With this assembly,-it will be seen that the comparatively rigid portion 20 of the supporting member 12, in conjunction with the ring 28, will serve to effectively maintain the coilsupport and its coil in a perfectly cylindrical form. In this embodiment of my invention, instead of clamping the terminals 18 upon the end of the cylindrical member, I mount any-suitable type of metallic member, designated by the numeral 30 in Fig. 8, upon the annular portion 20 of the flexible member 12. These members 30 form a metallic surface upon which the flexible leads 19 and the ends of the coil 13 may be readily soldered.

While I have, for the sake of clearness and in order to disclose my invention so that the same can be readily understood, described and illustrated specific devices and arrangements, I desire to have it understood that this invention is not limited to the specific means disclosed but may be embodied in other ways that will'suggest themselves, in view of this broad disclosure, to persons skilled in the art. It is believed that this invention is broadly new and it is desired to claim it as such so that all such changes as come within the scope of the appended claims are to be considered as part of this invention.

Having thus described my invention, what I claim and desire to secure by Letters Patent 1s 1. A diaphragm of the cone type for loud speakers comprising a cone having an open ing at its apex, a cylindrical member adapted to support a current-carrying winding and be disposed concentrically with respect to the opening at the a ex of said cone, and a\ member adapted to ll opening at the apex of said cone to flare the boundary thereof outwardly into intimate serrations 27 upon 26 are flared outinto the cylindrical ICL e pressed through the contact with the inside of said cylindrical member to thereby secure the parts together.

2. A diaphragm assembly for loud speakers comprising a cone of relatively stifi' material having an opening at. its apex, said cone being serrated about the boundary of said opening, a cylindrical member adapted to support a current-carrying winding and be disposed about said openlng, and 'a rigid means projecting through said opening adapted to telescope with the cylindrical member and expand the serrated boundary A of said opening in the cone into intimate contact with the interior of said cylindrical member whereby the cone and said member will be held firmly together.

3. A coil mounting for cone speakers comprising a cylindrical body portion having a flange formed thereupon by winding stri s of paper thereover, a flexible member exten ing edgewise outwardly from said cylindrical portion mounted adjacent one of said flanges and adapted to form a yielding support for said cylindrical portion, and means co-operating with said cylindrical portion adapted to flare the latter on the opposite side of said flexible member, whereby said flexible member will be held against displacement upon said cylindrical portion.

4. In a loud speaker, the combination of a cone having an opening at its apex, a cylindrical member adapted to support a currentcarrying winding, and a metallic member circular in outline adapted to be projected through the opening in said cone to expand the boundary thereof into contact with said cylindrical member, said metallic member being provided with flanges for stiffness and having a tight telescoping fit with the cylindrical member, whereby it will reinforce the joint between said cone and cylindrical member to maintain the joint cylindrical.

5. In a loud speaker of the electro-dynamic type, the combination of a cone, a.cylindrica1 member adapted to be secured to the apex of said cone. a flexible member extending edgewise and outwardly from said cylindrical member and forming a support therefor, a winding upon said cylindrical member, and means projecting into the apex of said cone adapted to expand the latter into intimate contact with said cylindrical member and said cylindrical member into intimate contact with said flexible member, wherebythe cylindrical member is secured upon said cone and said flexible support is secured upon said cylindrical member.

6. A method of assembling a driving unit for diaphragms of the cone type which comprises forming a cylindrical member of nonconducting material within an annular opening in a flexible supporting member so that the latter extends outwardly in an edge'wise manner from the cylindrical member, and winding upon said cylindrical member closely adjacent said flexible member a layer of paper with a suitable adhesive, and expanding the end of the cylindrical member within said supporting member, whereby the parts will be permanently secured together.

.7. A coil mounting for cone speakers comprising a cylindrical member adapted to be secured to the apex of a cone and supporta current-carrying winding, and a flat flexible supporting member extending edgewise from said cylindrical portion adapted to engage fixed supports, said supporting member being secured upon said cylmdrical portion intermediate the ends thereof by disposing it against a shoulder upon said cylindrical member and flaring the projecting end of the cylindrical member outwardly against said flexible member opposite said shoulder.

8. A support for the'coil-carrying end of' loud speaker cones comprising a cylindrical member adapted to be secured to the apex of the cone and support a current-carrying winding, a flat flexible member projecting edgewise outwardly from the surface of said cylindrical member and disposed in a plane at right angles to the axis thereof, and means for securing said flexible member to said cylindrical member consisting of a shoulder formed upon said cylindrical member contactin with one side of said flexible member and 1 aring said cylindrical member against said flexible member opposite said shoulder.

9. A diaphragm for loud speakers compris-i ing a cone of relatively stifl' material having a serrated opening at its apex, a cylindrical member adapted to be disposed about said opening and support a current-carrying winding, means consisting of a ring-shaped member adapted to pro ect through said opening and expand the serrated boundary thereof into intimate contact with the interior of said cylindrical member, a flexible supporting member adapted to extend outwardly from said cylindrical member in a plane at right angles to the axis thereof, and means (Bo-operating with said cylindrical member for securing said flexible member lt)hereupon at the end of the cylindrical memer. J" 10. A diaphragm and coil mounting for loud speakers of the electro-dynamic type, comprising a cone ofrelatively stifl' material having its apex open, a cylindrical member adapted to telescope over said cone at said opening and adapted to support a currentcarrying coil, a flexible member adapted to be mounted upon the end of said cylindrical member and extend outwardly therefrom in an edgewise manner, and a metallic ring adapted to be inserted through the opening of said cone to expand the latter and said cylindrical member into clamped engagement with said flexible member, whereby said cone, said cylindrical member and said flexible member will be securely held together.

11. A method of securinga, current-carry: ing coil having a centering support upon diaphragms of the cone type, which comprises serrating the open end of said cone and the adjacent end of the cylindrical current-carrying coil and flaring the serrated edges-so formed into tight engagement with each other within arelatively flexible and non-elasticmember extending in a plane at right angles thereto by the insertion of an annular me tallio member through the opening in said cone. a

EDWIN S. PRIDHAM. 

